Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$64.43	12.672%	$72.5946	$72.59	$72.60	$72.60
Purchase #2	$182.34	3.480%	$188.6854	$188.69	$188.70	$188.70
Purchase #3	$11.31	6.608%	$12.0574	$12.06	$12.05	$12.10
Purchase #4	$56.92	9.841%	$62.5215	$62.52	$62.50	$62.50
Purchase #5	$209.64	5.223%	$220.5895	$220.59	$220.60	$220.60
Purchase #6	$143.42	9.288%	$156.7408	$156.74	$156.75	$156.70
Purchase #7	$156.40	5.288%	$164.6704	$164.67	$164.65	$164.70
7 purchase totals =	$824.46		$877.8596	$877.86	$877.85	$877.90